Method for moving network elements with minimal network outages in an active atm network

ABSTRACT

A method for moving permanent virtual circuits in an ATM network with minimal downtime includes creating a list of the permanent virtual circuits to be moved; building a set of shadow permanent virtual circuits using the new ATM port and a temporary set of virtual path identifier and virtual circuit identifier pairs; moving a physical connection from the original ATM port to the new ATM port; deleting the permanent virtual circuits on the original ATM port; and changing the shadow permanent virtual circuits to use the original virtual path identifier and virtual circuit identifier pairs.

BACKGROUND

1. Field of the Invention

The present invention relates generally to broadband network management,and more particularly to management of asynchronous transfer modenetworks.

2. Background of the Invention

Traditionally, telecommunications service providers have offered basicservices such as local and long distance exchange services for voicecommunications. More recently, with the explosive growth of the Internetand other data services, telecommunications service providers haveexpanded beyond basic telephone services to the provision of very highbandwidth network services. Examples of such newer network servicesinclude, for example, digital subscriber line (DSL), asymmetric digitalsubscriber line (ADSL), integrated services digital network (ISDN)digital subscriber line (IDSL), and the like. The underlyingtransmission facility supporting such high bandwidth networks maycomprise an asynchronous transfer mode (ATM) network as shown in FIG.1A.

ATM network or “cloud” 10 in FIG. 1A comprises one or more ATM switches11-15. The switches may be interconnected in any suitable manner toprovide redundancy in the network and to ensure high speed transmissionof network packets. ATM switches are well-known in the art and areavailable from numerous switch vendors, including, for example, Lucent,Seimens and Northern Telecommunications. ATM switches typically comprisea processor, a memory and a backplane for supporting multiple networkcards in a plurality of slots 16 as shown in FIG. 1B. A network card,for example, network card 17, typically comprises multiple ports 18 forsupporting multiple communications paths. A distinct physicaltransmission cable, for example, a coaxial cable or fiber optic cable,may be connected to any given port on the network card. Each physicaltransmission cable carries thousands of logical circuits providing voiceand data service.

Network service providers (NSP) 20-22 are provided connectivity to theirend-users, subscribers 30, via ATM cloud 10 and central office DSLAM 40via a permanent virtual circuit (PVC). The network traffic for each NSPis carried via a plurality of PVCs. A PVC is a connection that isestablished from a source end point to a destination end point withoutthe ability of either end point to dynamically establish or release theconnection. PVCs are manually implemented and must be manually released.A PVC is a “permanent” circuit because each PVC defines an end-to-endpath for routing packets. However, the PVC is a “virtual” circuitbecause bandwidth from the cloud is utilized only when it is required.Each PVC is assigned a virtual path identifier (VPI) and a virtualconnection identifier (VCI), which together identify the virtualcircuit's end points, in accordance with well-known ATM standardspecifications. Each ATM packet transmitted in ATM network 10 includes aVPI field and a VCI field in a packet's header. Within ATM network 10,the combination of VPI/VCI must be unique for each PVC at the networkinterface point (the source end and destination end of the PVC) to theATM network, i.e., the physical network interface.

As described above, each ATM switch 11-15 supports multiple networkcards, and each network card supports multiple physical connections.However, in conventional ATM networks, the lack of tools for adequatelyplanning capacity changes in the network has proven to be a problem. Forexample, if every slot 16 on ATM switch 11 is configured with a networkcard supporting a eight ports (i.e., physical connections), and eachport was configured with over one thousand PVCs, an unacceptableperformance may result. One method for reducing such problems inconventional ATM networks has been to initially under-build the ATMnetwork. That is, for example, an ATM switch having twelve slots mayonly be filled with ten cards, and each card may only have connectionsgoing into six of the eight available ports.

While an ATM network capacity manager may have anticipated suchlimitations when the network was designed, an accurate capacity plan maynot be achievable without real-world network traffic being observed.This may be particularly true in situations where the demand for suchhigh-bandwidth network services could not be adequately predicted. Afteran ATM network has been established, any changes to the physical cardand port configuration require re-provisioning of every PVC affected.Accordingly, even moving one ATM physical connection from one switch toanother may require re-provisioning of thousands of PVCs, which meanshours and hours of service interruption.

Because each PVC must have a unique VPI/VCI at each network interface(it takes two network interfaces to create a destination and end point),the conventional method for re-provisioning a PVC required the followinggeneral steps:

1. select the new interface port;

2. unplug physical connection from old port and terminate to the newport; and

3. reassign, or relocate, the logical or virtual circuits to the newport.

This methodology is necessary due to the fact that the stationary end ofthe virtual circuit (the side not being relocated) cannot be manipulateddue to the restriction of the unique VPI/VCI for the interface port.

The problem with implementing these steps in a conventional manner isthat it may take several hours or even days to complete, resulting inunacceptable network downtime leading to customer service impairment.For example, an existing network may be configured as shown in the FIG.2A. In this example, multiple PVCs are assigned on the DSLAM end to porttwo on the card in slot five (denoted “C5/P2”) of ATM switch 200. TheNSP end of these PVC's are assigned to port three of the card in sloteight (C8/P3), port four of the card in slot 6 (C6/P4), and port two ofthe card in slot 8 (C8/P2) on ATM switch 200. If the ATM network managerneeds to move all of these PVCs terminated to the DSLAM through thecircuit connected to C5/P2 208 to a different card, for example, to portfour on the card in slot seven (C7/P4), the ATM manager must manuallyreassign each virtual circuit associated with 208 manually as follows:

1. As shown in FIG. 2B, each PVC must be manually relocated to the portC7/P4. For example, PVC 202 is originally assigned a connection betweenC5/P2 and C8/P3 202, as shown in FIG. 2A. At this point, the new PVC,PVC 204 is an inactive PVC that will not carry traffic on the ATMnetwork. Since the DSLAM 206 has not been connected to the new circuit209, the PVC is inactive and will not be available to the end-users.This step typically takes about three minutes to perform for each PVC.Accordingly, if there are one thousand affected PVCs, the total downtimefor this step alone will be fifty hours.

2. As shown in FIG. 2C, after the PVCs have been terminated to the newphysical connection, circuit connection 209 is created by unplugging 208from the old port. In other words, connection 208 is replaced byconnection 209; and

3. As shown in FIG. 2D, the final step in the process is to restoreservice to each PVC after the physical circuit has been reconnected. Atthis point in the process, PVC 204 is active and available to NSP 20.

Step 2 is repeated for each PVC that has been moved. Again, this steprequires about three minutes per PVC, resulting in a total downtime offifty hours for this step and creating the unacceptable servicecondition requiring a different business process to complete the task.

As the above example illustrates, the conventional methods for movingnetwork elements connected to an ATM cloud results in significantdowntime for ATM network customers. A need therefore exists for a methodof moving network elements with minimal network downtime for end-usersassociated with an ATM network.

SUMMARY OF THE INVENTION

The present invention provides a method for moving a plurality ofpermanent virtual circuits in an ATM network from a first ATM port to asecond ATM port. The method comprises: creating a list comprising theplurality of permanent virtual circuits to be moved, wherein the listcomprises a first plurality of virtual path identifier and virtualcircuit identifier pairs; building a plurality of shadow permanentvirtual circuits, wherein the plurality of shadow permanent virtualcircuits use the second ATM port, and wherein the plurality of shadowpermanent virtual circuits comprise a second plurality of virtual pathidentifier and virtual circuit identifier pairs; moving a physicalconnection from the first ATM port to the second ATM port; deleting theplurality of permanent virtual circuits on the first ATM port; andchanging the plurality of shadow permanent virtual circuits to use thefirst plurality of virtual path identifier and virtual circuitidentifier pairs.

The VPI/VCI restriction is on the end of the PVC circuit that is notrelocated. The restriction is unique to the stationary interface. TheVPI/VCI assignments on the relocated side of the PVC remain the same, asthe interface will move from Card 5 Port 2 to Card 7 Port 4 as describedin FIG. 2D. Thus, in accordance with the invention, coordination withthe NSP may sometimes be necessary since it “owns” the stationaryinterface and as such will need to allow the assignment of a ShadowVPI/VCI to be utilized for the duration of the relocation.

Thus, in other words, the invention creates a shadow PVC between astable or non-changing interface, and a changing interface. The shadowPVC is preferably made active as soon as the changing interface is movedfrom Card 5 Port 2 to Card 7 Port 4 as described in FIG. 2D. Therefore,the shadow VPINCI at the stationary interface is a key element to makethis process successful.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram illustrating an ATM network architecture.

FIG. 1B is a schematic diagram illustrating the backplane of a typicalATM switch.

FIGS. 2A-2D are schematic diagrams illustrating a conventional processfor moving network elements in an active ATM network.

FIG. 3 is a flow diagram of steps that may be performed to move networkelements in an active ATM network according to an embodiment of thepresent invention.

FIGS. 4A-4D are schematic diagrams illustrating a process to movenetwork elements in an active ATM network according to an embodiment ofthe present invention.

FIGS. 5A and 5B are schematic diagrams illustrating a process to movenetwork elements in an active ATM network according to an embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method for re-provisioning circuits ona digital subscriber line access multiplexer (DSLAM) in an activeasynchronous transfer mode (ATM) network with minimal service outagesfor the subscribers being served via the affected circuits. The flowdiagram shown in FIG. 3 shows exemplary steps that may be carried out tomove ATM network elements in an embodiment of the present invention.FIGS. 4A through 4D are schematic diagrams showing how these steps maybe implemented in an active ATM network.

In step 300 a list of all permanent virtual circuits on the affectedport and card is compiled. Referring the FIG. 4A, if the ATM networkmanager needs to move traffic from card five port two of ATM switch 400to card seven port four, the list would include the VPI/VCI for each PVCaffected. The list compiled in step 300 is used to build a set of“shadow” PVCs in step 302. The VPI/VCIs assigned to the new shadow PVCsare preferably determined after coordination with NSP 402. Typically,establishing shadow PVCs is accomplished with NSP coordination. In step304, shadow VPI/VCIs are built on the NSP side of ATM switch 400. Steps302 and 304 are illustrated in FIG. 4B. In that figure, shadow PVC 404,corresponding to existing PVC 406, is created with a VPI/VCI of 14/104.As shown in FIG. 4B, existing PVC 406 is still operational at this pointin the process. Shadow PVCs are built for each PVC affected by the move.

After all of the needed shadow PVCs have been provisioned, physical line408 (such as a DS3) is removed in step 306 and, as shown in FIG. 4C,physical line 410 is connected between DSLAM 412 and ATM switch 400. Itis noted that physical line 408 could be the same as physical line 410such that when line 408 is unplugged from card five port two, it may beplugged into card seven port four to become physical line 410.Alternatively, a new line may be used to complete the connection betweenDSLAM 412 and ATM switch 400. In step 308, the former PVCs are deletedon the port to be replaced, (i.e., card five, port two).

In step 310, an inventory system is updated to reflect the newconnection path for the DSLAM. In step 312, the shadow PVCs are madepermanent. This step involves approximately two minutes of downtime foreach PVC, but the down time is not cumulative. That is, each PVC is onlydown for the amount of time needed to change the temporary VPI/VCI backto original on the NSP-side of ATM switch 400. Thus, according to thepresent invention, a maximum network downtime for any given PVC will beunder approximately seventeen minutes, namely, about 15 minutes for step310 and about two minutes for step 312.

The present invention is not limited to operations with a single ATMswitch. For example, FIGS. 5A and 5B show how the present invention maybe used to move network elements from one ATM switch to another ATMswitch. In FIGS. 5A and 5B, all PVCs on card five port two of ATM switch500 are moved to card seven port four of ATM switch 502 according to thepresent invention. More specifically, as shown in FIG. 5A, a particularVPI/VCI is unique to each interface the NSP is connected to. Thus, asshown, the NSP is connected to VPI/VCI 14/104, but utilizing severaldifferent cards and ports. To reconfigure the connection, shadow PVCsare established defined by VPI/VCI pair 14/104. These shadow PVCstraverse inter-switch trunks 520 to pass between switches (e.g., 500 to502). Once the DSLAM connection is made to card seven port four (C7/P4),the original connection to C5/P2 is taken down. Thus, as described abovewith respect to moving connection within a single ATM switch, it is alsopossible to reconfigure connections among different switches withminimal downtime for each individual PVC.

The foregoing disclosure of the preferred embodiments of the presentinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Many variations andmodifications of the embodiments described herein will be apparent toone of ordinary skill in the art in light of the above disclosure. Thescope of the invention is to be defined only by the claims appendedhereto, and by their equivalents.

Further, in describing representative embodiments of the presentinvention, the specification may have presented the method and/orprocess of the present invention as a particular sequence of steps.However, to the extent that the method or process does not rely on theparticular order of steps set forth herein, the method or process shouldnot be limited to the particular sequence of steps described. As one ofordinary skill in the art would appreciate, other sequences of steps maybe possible. Therefore, the particular order of the steps set forth inthe specification should not be construed as limitations on the claims.In addition, the claims directed to the method and/or process of thepresent invention should not be limited to the performance of theirsteps in the order written, and one skilled in the art can readilyappreciate that the sequences may be varied and still remain within thespirit and scope of the present invention.

1. A method for moving a plurality of permanent virtual circuits in anATM network from a first ATM port to a second ATM port, said methodcomprising: creating a list comprising the plurality of permanentvirtual circuits to be moved, wherein the list comprises a firstplurality of virtual path identifier and virtual circuit identifierpairs; building a plurality of shadow permanent virtual circuits,wherein the plurality of shadow permanent virtual circuits use thesecond ATM port, and wherein the plurality of shadow permanent virtualcircuits comprise a second plurality of virtual path identifier andvirtual circuit identifier pairs; moving a physical connection from thefirst ATM port to the second ATM port; deleting the plurality ofpermanent virtual circuits on the first ATM port; and changing theplurality of shadow permanent virtual circuits to use the firstplurality of virtual path identifier and virtual circuit identifierpairs. 2-23. (canceled)